Insufflator assembly

ABSTRACT

An insufflator assembly, comprising: an insufflator comprising a delivery component ( 1 ) for delivering powder into an airway of an animal, a metering component ( 3 ) for providing a dose of powder (P) to the delivery component ( 1 ) and an inlet for receiving a stream of gas; and means for providing a stream of gas to the inlet of the insufflator so as to carry the dose of powder (P) into the airway of the animal, the means comprising a chamber ( 45 ) of a predetermined volume for containing gas at a predetermined pressure above atmospheric, a pressurized gas source ( 9 ) for providing gas of a predetermined pressure to the chamber ( 45 ), a first valve ( 47 ) for selectively connecting the chamber ( 45 ) to the pressurized gas source ( 9 ) and a second valve ( 49 ) for selectively connecting the chamber ( 45 ) to the inlet of the insufflator.

The present invention relates to an insufflator and an insufflatorassembly incorporating the same.

Insufflator assemblies are known for blowing or forcing doses of powdercontaining medicament into the lungs of animals. In particular,insufflator assemblies are used during pharmaceutical trials to deliverpowder containing medicament into the lungs of small animals, such asmice.

The dose of powder delivered to small animals is particularly small,typically in the range of from 20 to 25 μg. As such, it is difficultboth to measure a dose of powder accurately and to provide a dose ofpowder in such a manner that the entire dose of powder is carried intothe lungs of an animal.

In addition, the lungs of small animals are comparatively small, suchthat only a small volume of air can be used to deliver a dose of powder.Typically, for mice, the tidal volume, that is the volume of air passinginto and out of the lungs in each breath, is only about 0.15 ml. Assuch, it is difficult to provide an air flow which will carry the entiredose of powder into the lungs of an animal without exceeding thecapacity of the lungs of the animal.

One known insufflator assembly comprises a sample chamber connectedbetween a delivery tube and a syringe. The sample chamber, which is ofrelatively large dimension, comprises two halves which are separated toload a dose of powder thereinto. In use, a dose of powder is loaded intothe sample chamber and the delivery tube is then inserted into an airwayof an animal, usually the laryngeal tract. The plunger of the syringe isthen pushed rapidly into the body thereof so as to drive a predeterminedvolume of air through the sample chamber and carry the dose of powderfrom the sample chamber through the delivery tube and into the lungs ofthe animal.

In this known insufflator assembly the characteristics of the air floware highly dependent upon how rapidly the user pushes the plunger of thesyringe into the body thereof. In addition, the loading of powder intothe sample chamber requires the user both to measure precisely a dose ofpowder and to ensure that the entire measured dose of powder is loadedinto the sample chamber. Further, it is difficult to ensure that theentire dose of powder is delivered into the lungs of the animal.

Accordingly, the present invention provides an insufflator assembly,comprising: an insufflator comprising a delivery component fordelivering powder into an airway of an animal, a metering component forproviding a dose of powder to the delivery component and an inlet forreceiving a stream of gas; and means for providing a stream of gas tothe inlet of the insufflator so as to carry the dose of powder into theairway of the animal, the means comprising a chamber of a predeterminedvolume for containing gas at a predetermined pressure above atmospheric,a pressurized gas source for providing gas of a predetermined pressureto the chamber, a first valve for selectively connecting the chamber tothe pressurized gas source and a second valve for selectively connectingthe chamber to the inlet of the insufflator.

The present invention also provides a method of providing a stream ofgas containing powder, comprising the steps of: pressurizing a chamberof a predetermined volume with gas at a predetermined pressure aboveatmospheric; sealing the chamber; and connecting the chamber to an inletof an insufflator loaded with a dose of powder so as to release thepressurized gas into the insufflator and entrain the dose of powder in astream of gas.

The present invention ensures that too great a volume of gas is notdriven into the lungs of an animal. Indeed, the present invention can beconfigured to use an optimum volume of gas. Furthermore, since theinsufflator assembly is triggered on the opening of only a single valve,the flow characteristics of the gas flow are substantially the same foreach delivery. In particular, the flow characteristics are independentof the actions of a user.

The flow characteristics are particularly suited to powder delivery,since, on opening the second valve, gas of high pressure and highvelocity is immediately released. In contrast, in known insufflatorassemblies, there is a time lag while the pressure and the velocity ofthe gas flow builds up, such that the initial flow of gas isinsufficient to carry powder and is hence wasted. The initial highpressure and high velocity gas flow achieved by the present invention isparticularly effective in deagglomerating a packed dose of powder.

Preferably, the volume of gas delivered is from 1 to 2 ml.

The valves may be mechanical, but when the valves are any of pneumatic,electrical or magnetic, the insufflator assembly is more readilycontrollable. Preferably, at least the second valve should be aquick-opening valve.

In a preferred embodiment the second valve is connected to theinsufflator by tubing of small bore and short length. In this way, ahigh pressure and high velocity gas flow is most effectively provided tothe insufflator. This is because the dead space downstream of thechamber is minimized and there is only a small volume of gas in thetubing to be compressed, which compression will absorb part of theenergy of the gas flow.

The present invention further provides an insufflator assembly,comprising: an insufflator for insertion into an airway of an animal andfor delivering a dose of powder into the airway of the animal, theinsufilator comprising a tube with two open ends; and a loadingcomponent comprising an elongate member having an end face for insertioninto one end of the tube and for movement to a predetermined positionproximate the other end of the tube so as to define a space between theother end of the tube and the end face of the elongate member, whichspace is in use filled with a dose of powder.

The present invention still further provides a method of loading a doseof powder into an insufflator comprising a tube with two open ends,comprising the steps of: inserting an elongate member of a loadingcomponent into one end of the tube, the elongate member having an endface; moving the end face of the elongate member through the tube to apredetermined position proximate the other end of the tube; and fillinga space in the tube between the other end of the tube and the end faceof the elongate member with a dose of powder.

In this way, a dose of powder is loaded directly into the tube fromwhich it is delivered. Thus, additional steps of transferring a dose ofpowder intact to a delivery device are avoided. Furthermore, as the tubeis of small dimension, the dose of powder may be accurately selectedwith relative ease by varying the volume of the space defined in thetube. In a preferred embodiment the volume of the space is set so as toprovide a dose of powder of from 20 to 25 μg.

In a preferred embodiment the insufflator further comprises a furthertube having two open ends, one end being for insertion into the airwayof the animal and the other end being connectable with the other end ofthe first-mentioned tube.

The present invention yet further provides an insufflator for deliveringa dose of powder into an airway of an animal, comprising: a first tubehaving two open ends, one end being for insertion into an airway of ananimal; and a second tube having two open ends, one end for receiving astream of gas and the other end being in use loaded with a dose ofpowder and connected to the other end of the first tube.

The present invention still yet further provides a method of providing adose of powder in an insufflator for subsequent dispersion in a streamof gas, comprising the steps of: providing first and second connectabletubes; filling one end of one tube with a dose of powder; and connectingthe one end of the one tube to one end of the other tube.

In this way, a dose of powder is provided directly in the flow paththrough the insufflator. In particular, the dose of powder is located atthe inlet of the first tube such that the dose of powder can bedelivered effectively therethrough.

Preferably, the other end of the second tube is inserted into the otherend of the first tube.

The present invention contemplates for the first time that the airwayswith which the insufflator may be used include nasal passageways andthat powder containing medicament may be delivered to the nasalcavities. Thus, the present invention extends to a method of deliveringpowder containing medicament to nasal cavities by inserting aninsufflator into a nasal passageway.

It will be appreciated that whilst the present invention is described inrelation to use with animals the present invention can equally be usedwith humans.

Medicaments suitable for administration by the present invention are anywhich may be delivered into airways and include for exampleβ2-adrenoreceptor agonists, for example, salbutamol, terbutaline,rimiterol, fenoterol, reproterol, adrenaline, pirbuterol, isoprenaline,orciprenaline, bitolterol, salmeterol, formoterol, clenbuterol,procaterol, broxaterol, picumeterol, TA-2005, mabuterol and the like,and their pharmacologically acceptable esters and salts; anticholinergicbronchodilators, for example, ipratropiumn bromide and the like;glucocorticosteroids, for example, beclomethasone, fluticasone,budesonide, tipredane, dexamethasone, betamethasone, fluocinolone,triamcinolone acetonide, mometasone and the like, and theirpharmacologically acceptable esters and salts; antiallergic medicaments,for example, sodium cromoglycate and nedocromil sodium; expectorants;mucolytics; antihistamines; cyclooxygenase inhibitors; leukotrienesynthesis inhibitors; leukotriene antagonists; phospholipase-A2 (PLA2)inhibitors; platelet aggregating factor (PAF) antagonists andprophylactics of asthma; antiarrhythmic medicaments; tranquilisers;cardiac glycosides; hormones; antihypertensive medicaments; antidiabeticmedicaments; antiparasitic medicaments; anticancer medicaments;sedatives; analgesic medicaments; antibiotics; antirheumaticmedicaments; immunotherapies; antifungal medicaments; antihypotensionmedicaments; vaccines; antiviral medicaments; proteins; polypeptides andpeptides, for example, peptide hormones and growth factors; polypeptidevaccines; enzymes; endorphines; lipoproteins and polypeptides involvedin the blood coagulation cascade; vitamins; and others, for example,cell surface receptor blockers, antioxidants, free radical scavengersand organic salts of N,N′-diacetylcystine.

Preferred embodiments of the present invention will now be describedhereinbelow by way of example only with reference to the accompanyingdrawings, in which:

FIG. 1 illustrates the principal elements of an insufflator assembly inaccordance with a first embodiment of the present invention;

FIG. 2 illustrates the delivery component of the insufflator of theinsufflator assembly of the first embodiment of the present invention;

FIG. 3 illustrates the metering component of the insufflator of theinsufflator assembly of the first embodiment of the present invention;

FIG. 4 illustrates the metering component of the insufflator and theloading component when fitted together of the insufflator assembly ofthe first embodiment of the present invention;

FIG. 5 illustrates the loading component of the insufflator assembly ofthe first embodiment of the present invention;

FIG. 6 illustrates the insufflator of an insufflator assembly inaccordance with a second embodiment of the present invention;

FIG. 7 illustrates the delivery component of the insufflator of theinsufflator assembly of the second embodiment of the present invention;

FIG. 8 illustrates the metering component of the insufflator of theinsufflator assembly of the second embodiment of the present invention;

FIG. 9 illustrates the metering component of the insufflator and theloading component when fitted together of the insufflator assembly ofthe second embodiment of the present invention; and

FIG. 10 illustrates the loading component of the insufflator assembly ofthe second embodiment of the present invention.

In a first embodiment the insufflator assembly comprises an insufflatorcomprising a delivery component 1 for delivering powder into thelaryngeal tract of an animal and a metering component 3 for providing adose of powder to the delivery component 1, a loading component 5 foruse in loading a dose of powder into the metering component 3 of theinsufflator and an air supply means comprising a firing unit 7 and apressurized air source 9 connectable to the insufflator for providing anair flow to carry the dose of powder into the lungs of the animal.

The delivery component 1 comprises a delivery tube 11 for insertion intothe laryngeal tract of an animal, which delivery tube 11 is preferably acannula similar to the needle of a syringe and may be metallic. One endof the delivery tube 11 is provided with a connector 13 having aninwardly tapered frusto-conical portion 15 for receiving the meteringcomponent 3. The other end of the delivery tube 11, which is insertedinto the laryngeal tract, is preferably provided with a conically,olived or droplet shaped portion 17 so as to minimise trauma to thelaryngeal tract during insertion. Preferably, the connector 13 is astandard syringe connector, such as a Luer connector.

The metering component 3 comprises a connector 19 having afrusto-conical portion 21 which is adapted to fit into and seal with thefrusto-conical portion 15 of the connector 13 of the delivery component1. The connector 19 further has an extension 23 in which is formed aperipheral groove 25. The metering component 3 further comprises ametering tube 27 which extends through the connector 19. One end of themetering tube 27, in this embodiment that end extending from the smallend on the connector 19, is shaped and dimensioned to locate within atleast an end part of the delivery tube 11 of the delivery component 1.

In this embodiment, as illustrated in FIG. 1, the outer dimension of themetering tube 27 is substantially the same as the inner dimension of thedelivery tube 11 such that the metering tube 27 and the delivery tube 11are generally in sealing engagement when the metering component 3 isfitted to the delivery component 1 and the metering tube 27 is insertedinto the delivery tube 11. In this way, a high pressure air flow isintroduced directly into the delivery tube 11 and it is thereforeunnecessary for the connection between the frusto-conical portions 15,21 of the connectors 13, 19 to withstand such pressures. Accordingly,whereas traditional Luer locks use stainless steel connectors, theconnectors 13, 19 can be formed from other materials, such as plasticsmaterials.

The loading component 5, which is used to load a dose of powder into themetering component 3, comprises an elongate member 29 having an end face31 with an outer dimension substantially the same as the inner dimensionof the metering tube 27 and a stop 33 adjustably mounted to one end ofthe elongate member 29. In this embodiment the stop 33 includes athrough slot 35 in which the elongate member 29 is slidable, with thestop 33 being fixed in position relative to the elongate member 29 byscrews 37 which are tightened against the elongate member 29. When theloading component 5 is fitted to the metering component 3, asillustrated in FIG. 4, the stop 33 restricts how far the elongate member29 is inserted into the metering tube 27. The length of the elongatemember 29 protruding beyond the stop 33 is selected such that a space 39of predetermined volume is defined by the inner surface of the meteringtube 27 and the end face 31 of the elongate member 29 at the distal endof the metering tube 27.

The loading component 5 further comprises a sprung component 41 whichacts to retain the loading component 5 in a fixed position relative tothe metering component 3 when fitted thereto. One end 43 of the sprungcomponent 41, in this embodiment a U-shaped sprung member, isresiliently biased towards the elongate member 29. When the elongatemember 29 is inserted into the metering tube 27, the end 43 of thesprung component 41 is located in the peripheral groove 25 in theextension 23 of the connector 19. In this way, the loading component 5is securely retained relative to the metering component 3 during thestep of filling the space 39 with a dose of powder.

As will be apparent, the end face 31 of the elongate member 29 shouldgenerally seal with the inner surface of the metering tube 27 at leastin so far as is necessary to prevent any significant amount of powderpassing beyond the end face 31. Preferably, for the purposes ofproviding a good seal and imparting linearity to the adjustment of thevolume of the space 39 with movement of the elongate member 29, the endsection of the inner surface of the metering tube 27 is of uniformcross-section. The length of this end section need only be as long asthat of the required length of adjustment. Nevertheless, in a preferredembodiment, the entire length of the inner surface of the metering tube27 is of uniform cross-section and the elongate member 29 comprises arod having an outer surface with a cross-section substantially the sameas that of the inner surface of the metering tube 27. In anotherembodiment the end face 31 of the elongate member 29 can be providedwith a seal, such as a cup seal. However, whilst providing an excellentseal, this arrangement tends to make dosing accuracy more difficult todetermine.

In use, with the loading component 5 fitted to the metering component 3,the space 39 is filled with a predetermined dose of powder P. Typically,the space 39 is filled by dipping the distal end of the metering tube 27into powder so as to pack the space 39 with a dose of powder P. Inpractice, the distal end of the metering tube 27 is dipped more thanonce, preferably 20 to 30 times and more preferably 40 or more times, toensure good packing. In a preferred embodiment the distal end of themetering tube 27 is actually pressed against a surface, preferably anelastic surface, such that powder is forced into the space 39. Ideally,powder would be provided in a small cap-like container with arubber-like base or insert.

The metering component 3 may be fitted to the delivery component 1before or after the loading component 5 is removed from the meteringcomponent 3. Owing to the nature of the very fine powder used, the doseof powder P will remain in a packed state within the metering tube 27even if the loading component 5 is removed from the metering component 3before fitting of the metering component 3 to the delivery component 1.

The firing unit 7 comprises a chamber 45, in this embodiment provided bya tube, of predeterminable volume having an inlet to which is provided afirst valve 47 and an outlet which is provided a second valve 49. Theuse of a tube enables small volumes to be accurately determined and alsoensures an air flow with good flow characteristics. The chamber 45 maybe of fixed volume or may incorporate means for varying the volumeaccording to particular requirements. In this embodiment the valves 47,49 are magnetic valves, but any other easily controlled valves could beused. The inlet of the chamber 45 is connected via the first valve 47 tothe pressurized air source 9 with tubing 51. The outlet of the chamber45 is connected via the second valve 49 to the metering tube 27 of themetering component 3 of the insufflator with flexible tubing 53.

In use, with the second valve 49 closed and the first valve 47 open, thepressurized air source 9 fills the chamber 45 with air at apredetermined pressure. Once a stable condition has been reached, thefirst valve 47 is then closed. At this point, the firing unit 7 is readyfor operation to drive the dose of powder P from the delivery tube 11.To drive the dose of powder P from the delivery tube 11, the secondvalve 49 is opened, thereby releasing the predetermined volume ofpressurized air through the tubing 53, into the metering tube 27 whereit entrains the dose of powder P and then out of the delivery tube 11.

FIG. 6 illustrates the insufflator of an insufflator assembly inaccordance with a second embodiment of the present invention. Thisinsufflator is structurally quite similar to the insufflator of theabove-described embodiment and in order not to unnecessarily duplicatedescription only the differences will be described. Operation of theinsufflator is the same as that of the above-described embodiment.

In this embodiment the end of the delivery tube 11 of the deliverycomponent 1 into which the metering tube 27 of the metering component 3is fitted is tapered and the metering tube 27 has an outer dimensionwhich is greater than the inner dimension of the delivery tube 11. Inthis way, the metering tube 27 abuts the tapering section of thedelivery tube 11 when the metering component 3 is fitted to the deliverycomponent 1.

In this embodiment, as illustrated in FIG. 9, the sprung component 41 ofthe loading component 5 comprises a spring and the metering component 3includes a bent ring 55 instead of the extension 23. By engaging one endof the spring around the bent ring 55 the loading component 5 can besecurely retained in relation to the metering component 3 during thestep of loading a dose of powder P into the space 39.

It will be appreciated that the flow characteristics of the air flowdelivered by the above-described insufflator assemblies willsubstantially be the same for each delivery, since there is no manualaction required to pump air through the insufflator. Furthermore, theair flow provided is instantly both of high pressure and high velocity.Thus, a small volume of air, for instance 1 to 2 ml, is effectively usedto deagglomerate the dose of powder P in the space 39 and carry the sameinto an airway of an animal. This effect is maximized by using a smallbore tube for the tubing 53 so as to minimize the dead space downstreamof the chamber 45.

In another embodiment the outer dimension of the metering tube 27 of themetering component 3 can be smaller than the inner dimension of thedelivery tube 11 of the delivery component 1. A sealing fit of thedelivery tube 11 and the metering tube 27 is not essential as thefrusto-conical portions 15, 21 of the connectors 13, 19 can beconfigured to provide a hermetic seal, and thus any air introduced intothe metering tube 27 can only pass through the delivery tube 11.

In a further embodiment the metering tube 27 may have generally the sameor larger inner and outer dimensions than the delivery tube 11. In thisembodiment, however, one or both of the end of the metering tube 27 andthe end of the delivery tube 11 which are connected to one another aretapered such that the end of the metering tube 27 is located within thedelivery tube 11.

In a still further embodiment one or both of the delivery tube 11 andthe metering tube 27 are tapered along either a portion or the entirelength.

In each of the above-described embodiments, when the connector 19 of themetering component 3 is fitted to the connector 13 of the deliverycomponent 1, the end of the metering tube 27 is inserted into thedelivery tube 11. The frusto-conical portions 15, 21 of the connectors13, 19 help guide the end of the metering tube 27 into the delivery tube11, as does, in the second-described embodiment, the inwardly taperingend section of the delivery tube 11.

In a particularly preferred embodiment the inner dimension of themetering tube 27 is no greater than the inner dimension of the deliverytube 11. Thus, when the metering component 3 is fitted to the deliverycomponent 1, a dose of powder P is actually provided within the deliverytube 11 or at least in a direct flow path with the delivery tube 11. Itis particularly advantageous for the inner dimension of the deliverytube 11 to be the same or larger than the inner dimension of themetering tube 27, since there is then no obstruction to powder leavingthe metering tube 27 and entering the delivery tube 11. This arrangementcontrasts with that of known insufflators where the air flow is resistedand constricted in flowing from a relatively large dimension samplechamber into a delivery tube. Furthermore, the known insufflators, inhaving sample chambers of a size sufficient to allow a user manually toload a dose of powder thereinto, suffer from the drawback that the airflow for carrying the powder is significantly reduced in pressure andvelocity. Not only does this reduce the ability of the air flow to pickup the powder from the sample chamber, but also can mean that thesmaller dimension delivery tube may provide such a back pressure thatthe air flow cannot carry the powder, particularly when agglomerated,into the delivery tube. This, in turn, can result in blocking of theopening to the delivery tube.

In a yet further embodiment, in order to provide for adjustment of thelength of the elongate member 29 extending from the stop 33, theelongate member 29 can be screwed into the stop 33, possibly with theuse of a securing lock nut.

In another alternative embodiment, as a modification of thefirst-described embodiment, the extension 23 of the connector 19 can beomitted and instead an olive can be fitted to the metering tube 27 toact as the part behind which the sprung component 41 of the loadingcomponent 5 engages.

Finally, it will be understood by a person skilled in the art that thepresent invention has been described in its preferred embodiments andcan be modified in many different ways without departing from the scopeof the invention as defined in the appended claims. For example,although in the described embodiments elements are used which have acircular cross-section other cross-sections can be used.

What is claimed is:
 1. An insufflator assembly, comprising: aninsufflator comprising a delivery component for delivering powder intoan airway of an animal, and a metering component containing apredetermined dose of powder for delivery to the delivery componentwherein the metering component comprises an inlet for receiving a streamof gas and an outlet connected to said delivery component; and a firingunit for providing a volume of pressurized gas to the inlet so as tocarry the dose of powder into the airway of the animal wherein thefiring unit comprises a chamber of a predetermined volume for containinggas at a predetermined pressure above atmospheric and the chambercomprises a first valve for selectively connecting the chamber to apressurized gas source which provides gas and a second valve forselectively connecting the chamber to the inlet of the meteringcomponent, whereby both valves can be closed after said chamber has beenfilled with pressurized gas and said second valve can then be opened todeliver a predetermined volume of air through said metering componentand said delivery component to deliver said dose of powder.
 2. Theinsufflator assembly according to claim 1, wherein the predeterminedpressure is selectively adjustable.
 3. The insufflator assemblyaccording to claim 1 or 2, wherein the predetermined volume of thechamber is selectively adjustable.
 4. The insufflator assembly accordingto claim 1, wherein the chamber comprises an elongate tube.
 5. Theinsufflator assembly according to claim 1, wherein the meteringcomponent includes an elongate metering tube having a first open end anda second open end.
 6. The insufflator assembly according to claim 5,further comprising a loading component comprising an elongate memberhaving an end face for insertion into a first end of the metering tubeand for movement to a predetermined position proximate a second end ofthe metering tube so as to define a space between the second end of themetering tube and the end face of the elongate member, which space is inuse filled with a dose of powder.
 7. The insufflator assembly accordingto claim 6, wherein the loading component further comprises a stop whichis fixed to the elongate member and is configured so as to abut thefirst end of the metering tube when the end face of the elongate memberis at the predetermined position.
 8. The insufflator assembly accordingto claim 7, wherein the stop is movable relative to the elongate memberso as to provide for adjustment of the distance between the stop and theend face of the elongate member.
 9. The insufflator assembly accordingto claim 8, wherein the stop includes a slot in which the elongatemember is slideable and a fixing mechanism for fixing the stop relativeto the elongate member.
 10. The insufflator assembly according to claim9, wherein the fixing mechanism comprises at least one screw which inuse extends into the stop and selectively abuts a side surface of theelongate member.
 11. The insufflator assembly according to claim 7,wherein the loading component further comprises a sprung componenthaving a first end which is engageable with a part of the insufflator soas to retain the stop in abutment with the first end of the meteringtube.
 12. The insufflator assembly according to claim 11, wherein themetering component includes a part connected to the metering tube andthe sprung component of the loading component engages the part when theloading component is fitted to the metering component.
 13. Theinsufflator assembly according to claim 5, wherein the deliverycomponent includes an elongate delivery tube having a first and a secondend, the first end for insertion into the airway of the animal and thesecond end being connectable with the second end of the metering tube.14. The insufflator assembly according to claim 13, wherein the secondend of the delivery tube and the second end of the metering tube areconnectable by means of a Luer connection.
 15. The insufflator assemblyaccording to claim 14, wherein the second end of the metering tube isconfigured so as to be insertable into the second end of the deliverytube.
 16. A method of providing a stream of gas containing powder,comprising the steps of: providing an insufflator comprising a meteringcomponent loaded with a dose of powder; and providing a stream of gas toan inlet of the insufflator so as to entrain the dose of powder;characterized in that the step of providing a stream of gas comprisesthe steps of pressurizing a chamber of a predetermined volume with gasat a predetermined pressure above atmospheric, sealing the chamber andconnecting the chamber to the inlet of the insufflator and releasing thepressurized gas from said chamber into the insufflator and entrainingthe dose of powder in a pressurized volume of gas.
 17. The methodaccording to claim 16, wherein the steps of sealing the chamber andconnecting the chamber to the inlet of the insufflator include the stepsof operating a first valve for selectively connecting the chamber to apressurized gas source and operating a second valve for selectivelyconnecting the chamber to the inlet of the insufflator.
 18. The methodaccording to claim 16, further comprising the step of setting the volumeof the chamber to a predetermined volume.
 19. The method according toclaim 16, further comprising the step of setting the pressure of gas inthe chamber to a predetermined pressure.
 20. The method according toclaim 16, wherein the insufflator includes an elongate metering tubehaving open ends, and the step of providing an insufflator loaded with adose of powder comprises the steps of inserting an elongate memberhaving an end face into one end of the metering tube, moving the endface of the elongate member through the metering tube to a predeterminedposition proximate the other end of the metering tube such as to definea space between the other end of the metering tube and the end face ofthe elongate member and filing the space in the metering tube with adose of powder.
 21. The method according to claim 20, wherein theloading component further comprises a stop which is fixed to theelongate member, the elongate member being inserted into the meteringtube until the stop abuts the one end of the metering tube and the endface of the elongate member is at the predetermined position.
 22. Themethod according to claim 21, further comprising the step of adjustingthe distance between the end face of the elongate member and the stop soas to adjust the volume of the space in the metering tube.